Methods and arrangements for downlink multi-carrier power control in a wireless communications system

ABSTRACT

A method, User Equipment (UE), and radio base station or NodeB for controlling the downlink transmit power of a Fractional Downlink Physical Control Channel (F-DPCH) in a multi-carrier High-Speed Packet Access (HSPA) system. Single-carrier Transmit Power Control (TPC) commands are modified to support different kinds of multi-carrier scenarios. The UE defines at least one TPC command for adjustment of the transmit power of the F-DPCH of N downlink carriers, the number of TPC commands being equal to or less than N, and transmits the TPC command(s) on at least one of M uplink carriers. The NodeB receives the TPC command(s) and adjusts the transmit power of the F-DPCH of the N downlink carriers based on the received TPC command(s).

This application claims the benefit of U.S. Provisional ApplicationNo.61/048,319, filed Apr. 28, 2008, the disclosure of which is fullyincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the area of wireless communications,and especially to F-DPCH power control in a multi-carrier UniversalMobile Telecommunication System. More specifically, the inventionrelates to a method of F-DPCH power control in a radio base station andin a user equipment, as well as to a radio base station and a userequipment.

BACKGROUND

The Universal Mobile Telecommunication System (UMTS), also referred toas the third generation (3G) system or the wideband code divisionmultiplexing access (WCDMA) system, is designed to succeed GSM. UMTSTerrestrial Radio Access Network (UTRAN) is the radio access network ofa UMTS system.

High-Speed Downlink Packet Access (HSPDA) is an evolution of UTRANbringing further enhancements to the provisioning of packet-dataservices both in terms of system and end-user performance. The downlinkpacket-data enhancements of HSDPA are complemented with Enhanced Uplink(EUL), also known as High-Speed Uplink Packet Access (HSUPA). EULprovides improvements in the uplink capabilities and performance interms of higher data rates, reduced latency, and improved systemcapacity, and is therefore a natural complement to HSDPA. HSDPA and EULare often jointly referred to as High-Speed Packet Access (HSPA). In theHSPA architecture, a user equipment (UE) 150 is wirelessly connected toa radio base station, i.e. a NodeB 130, as illustrated in FIG. 1.

The operation of WCDMA/HSPA on multiple 5 MHz frequency blocks—so calledcarriers—used simultaneously for one given UE, is one further step ofevolving WCDMA and HSPA. This mode of operation is often referred to asmulti-carrier HSPA.

A multi-carrier connection with frequency division duplex (FDD) can bedescribed as a set of downlink carriers linked to a set of uplinkcarriers for a given UE. The downlink carriers can be adjacent ornon-adjacent in the frequency domain, and the same holds for the uplinkcarriers. More generally speaking, the carriers do not need to be in thesame frequency band, and time division duplex (TDD) bands could also beused as part of the multi-carrier operation. The number of downlinkcarriers may also be different from the number of uplink carriers in amulti-carrier connection for a given UE. If there is one uplink carrier,the number of downlink carriers can for example be two or more. Theopposite with more uplink carriers than downlink carriers is alsopossible. Hereinafter, the “multi-carrier symmetry” of a connectionrefers to the number of uplink and downlink carriers in themulti-carrier connection for a given UE.

Conventionally, one anchor carrier can be defined in uplink and one indownlink, in a multi-carrier connection. The remaining carriers (uplinkand downlink) can then be referred to as non-anchor (NA) carriers. Forexample, most of the control signaling can be carried on the anchorcarrier, while the non-anchor carriers carry only the data channels andnecessary control signaling channels that cannot be carried on theanchor carrier.

In prior art, WCDMA/HSPA systems make use of a mechanism to control thetransmit power of the fractional downlink physical control channel(F-DPCH), which is the downlink channel that carries transmit powercontrol commands from the NodeB to the UE used by the UE to adjust thetransmit power of the uplink carrier. With this mechanism the transmitpower control (TPC) commands are defined by the UE, based onmeasurements of the signals received from the NodeB. The TPC command canindicate either “up” corresponding to a power increase of e.g. 1 dB, or“down” corresponding to a power decrease. The TPC commands aretransmitted on an uplink control channel, in order for the NodeB toadjust the downlink transmit power of the F-DPCH.

In a conventional multi-carrier HSPA system, there can be differentmulti-carrier symmetries with multiple downlink carriers and/or multipleuplink carriers for a given UE, as described above. The differentcarriers may use adjacent or non-adjacent frequency bands. Amulti-carrier system also operates in soft handover scenarios. In allmulti-carrier systems, there is a need to control the transmission powerof the downlink carriers' F-DPCH. Downlink power control mechanisms hasto be defined, going beyond the mechanisms used in single-carriersystems with only one uplink and one downlink carrier, e.g. becausechannel conditions may differ between different (potentiallynon-adjacent) downlink carriers. Thus, there is a need to provide anefficient and reliable control of the downlink transmit power of F-DPCHin a multi-carrier HSPA system, regardless of e.g. the multi-carriersymmetry and the used frequency bands for the different carriers.

SUMMARY

The object of the present invention is to address the problem outlinedabove, and this object and others are achieved by the method and thearrangement according to the appended independent claims, and by theembodiments according to the dependent claims.

A basic concept of the invention is to adapt the TPC command mechanismfor F-DPCH transmit power control, used in single-carrier systems, tosupport different kinds of multi-carrier scenarios, including thedifferent soft-handover scenarios.

Thus in accordance with a first aspect of the present invention, amethod of downlink transmit power control in a user equipment of amulti-carrier wireless communication system is provided. The userequipment receives on N downlink carriers and transmits on M uplinkcarriers in the communication with at least one radio base station,where the sum of N and M is equal to or larger than three. The methodcomprises the step of defining at least one TPC command to be used bythe radio base station for adjusting the transmit power of the F-DPCH onthe N downlink carriers, the number of defined TPC commands being equalto or lower than N. It also comprises the step of transmitting thedefined at least one TPC command on at least one of the M uplinkcarriers.

In accordance with a second aspect of the present invention, a method ofdownlink transmit power control in a radio base station of amulti-carrier wireless communication system is provided. The radio basestation transmits on N downlink carriers and receives on M uplinkcarriers in the communication with at least one user equipment, wherethe sum of N and M is equal to or larger than three. The methodcomprises the step of receiving at least one TPC command on at least oneof the M uplink carriers from the at least one user equipment, thenumber of received TPC commands being equal to or lower than N. It alsocomprises the step of adjusting the transmit power of the F-DPCH on theN downlink carriers based on the received at least one TPC command.

In accordance with a third aspect of the present invention, a userequipment of a multi-carrier wireless communication system is provided.The user equipment is arranged to receive on N downlink carriers andtransmit on M uplink carriers in the communication with at least oneradio base station, where the sum of N and M is equal to or larger thanthree. The user equipment comprises means for defining at least one TPCcommand to be used by the radio base station for adjusting the transmitpower of the F-DPCH on the N downlink carriers, the number of definedTPC commands being equal to or lower than N. It also comprises means fortransmitting the defined at least one TPC command on at least one of theM uplink carriers.

In accordance with a fourth aspect of the present invention, a radiobase station of a multi-carrier wireless communication system isprovided. The radio base station is arranged to transmit on N downlinkcarriers and receive on M uplink carriers in the communication with theat least one user equipment, where the sum of N and M is equal to orlarger than three. The radio base station comprises means for receivingat least one TPC command on at least one of the M uplink carriers fromthe at least one user equipment, the number of received TPC commandsbeing equal to or lower than N. It also comprises means for adjustingthe transmit power of the F-DPCH on the N downlink carriers based on thereceived at least one TPC command.

An advantage of the embodiments of the present invention is that theyprovide a solution for downlink power control in a multi-carrier system.Another advantage of the embodiments of the present invention is thatthe different uplink carriers are used in a way that optimizes thereliability of the power control commands in the case of frequencyselective uplink channel conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically a part of a single- or multi-carrierWCDMA/HSPA system.

FIG. 2 a-2 f illustrates schematically different embodiments of thepresent invention applied in some examples of multi-carrier connectionswith different carrier symmetries.

FIGS. 3 a-3 f are flowcharts of the methods of the radio base stationand the UE according to different embodiments of the present invention.

FIG. 4 illustrates schematically the NodeB and UE according toembodiments of the present invention.

DETAILED DESCRIPTION

In the following, the invention will be described in more detail withreference to certain embodiments and to accompanying drawings. Forpurposes of explanation and not limitation, specific details are setforth, such as particular scenarios, techniques, etc., in order toprovide a thorough understanding of the present invention. However, itwill be apparent to one skilled in the art that the present inventionmay be practised in other embodiments that depart from these specificdetails.

Moreover, those skilled in the art will appreciate that the functionsand means explained herein below may be implemented using softwarefunctioning in conjunction with a programmed microprocessor or generalpurpose computer, and/or using an application specific integratedcircuit (ASIC). It will also be appreciated that while the currentinvention is primarily described in the form of methods and devices, theinvention may also be embodied in a computer program product as well asin a system comprising a computer processor and a memory coupled to theprocessor, wherein the memory is encoded with one or more programs thatmay perform the functions disclosed herein.

The present invention is described herein by way of reference toparticular example scenarios. In particular the invention is describedin a non-limiting general context in relation to a multi-carrier HSPAsystem. It should though be noted that the invention and its exemplaryembodiments may also be applied to other types of radio accesstechnologies with similar characteristics to HSPA in terms of powercontrol, such as LTE, WiMAX and UTRA TDD. Furthermore, the presentinvention is described with the help of examples of differentmulti-carrier symmetries. However, the present invention is not limitedto these examples. Any other multi-carrier symmetry will also besupported.

The present invention relates to methods and arrangements that enablecontrol of the F-DPCH transmit power in a multi-carrier HSPA system.This is achieved by using the concept of TPC commands (used insingle-carrier systems), adapted to support different kinds ofmulti-carrier scenarios, including the soft handover scenarios. Anobject is to provide an efficient and reliable power control mechanismfor F-DPCH in a multi-carrier system, regardless of e.g. themulti-carrier symmetry and the frequency bands used for the differentcarriers.

In the present invention, one or more TPC commands are defined in the UEto control the transmit power of the F-DPCH on the downlink carriers,based on measurements of the signals from the NodeB. These TPC commandsare then transmitted on the uplink carriers to the NodeB in differentways depending on the number of uplink carriers and on the number ofdefined TPC commands. The NodeB will receive the TPC command(s) andadjust the downlink power in different ways depending on the type of TPCcommand(s) and the multi-carrier symmetry.

In a first embodiment of the present invention, the TPC commands aretransmitted on one or more uplink control channels on the uplinkcarriers. If more than one TPC command is to be transmitted on oneuplink carrier (this case is further explained below), then each TPCcommand is mapped on a separate channel on that carrier. It is alsopossible to define a new control channel that can carry more than oneTPC commands.

One main principle of the present invention is that the number of TPCcommands that are defined and transmitted on the uplink shall be equalto or less than the number of downlink carriers to control. This meansthat for the case of one downlink carrier and two or more uplinkcarriers, only one TPC command shall be defined and transmitted on theuplink (i.e. on one or more uplink carriers) to control the downlinkF-DPCH. In the case of multiple downlink carriers, the following twoalternative embodiments are possible.

-   -   1. One TPC command per downlink carrier is defined and        transmitted, in order for the NodeB to adjust the power of each        downlink carrier's F-DPCH separately. The number of TPC commands        thus corresponds to the number of downlink carriers.    -   2. One single common TPC command—i.e. common for all downlink        carriers' F-DPCH—is defined and transmitted in order for the        NodeB to adjust the power of all the downlink carriers' F-DPCH        in the same way. In this embodiment, there are different        alternatives on how to define the common TPC command. In a first        alternative embodiment A, a TPC command valid for one of the        downlink carrier's F-DPCH, e.g. the anchor carrier's F-DPCH, is        used to power control all downlink carriers' F-DPCH in the same        way. In a second alternative embodiment B, the different TPC        commands valid for all the downlink carriers' F-DPCH are        combined according to some pre-defined combination rule. In one        embodiment the pre-defined combination rule is the “or of down”        rule, stating that the combined value indicates “up” when all        TPC commands indicate “up”, and indicates “down” if at least one        of the TPC commands indicates “down”. In an alternative        embodiment the pre-defined combination rule is the “or of up”        rule, stating that the combined value indicates “down” when all        TPC commands indicate “down”, and indicates “up” if at least one        of the TPC commands indicates “up”.

A combination of the alternative embodiments 1 and 2 above is alsopossible, by using alternative embodiment 1 for one group of downlinkcarriers' F-DPCH, and alternative embodiment 2 for the rest of thedownlink carriers' F-DPCH. In the example with three downlink carriersand two uplink carriers, one TPC command is defined to control the powerof the two first downlink carriers' F-DPCH jointly (according toalternative embodiment 2 above) and one TPC command is defined tocontrol the third downlink carrier's F-DPCH separately (according toalternative embodiment 1 above) for instance.

The transmission of the TPC command(s) may also vary with the differentmulti-carrier symmetries, as it depends on the number of availableuplink carriers. In the case of alternative embodiment 1 above, thereare three different alternatives for the transmission of the TPCcommands, depending on if the number of uplink carriers M is largerthan, smaller than, or equal to the number N of downlink carriers'F-DPCH to power control. The number of downlink carriers N correspondsto the number of defined TPC commands to transmit. The threealternatives are described below:

-   -   i. When the number of uplink carriers M is equal to or larger        than the number of downlink carriers N to control, each TPC        command is transmitted on a separate uplink carrier.    -   ii. However, when the number of uplink carriers M is larger than        the number of downlink carriers N to control, one TPC command        (e.g. the TPC command for the anchor downlink carrier) may be        transmitted on more than one uplink carrier to control one of        the downlink carrier's F-DPCH. The NodeB will then adjusts the        transmit power for the downlink carrier's F-DPCH according to a        combination of the commands received on the different uplink        channels. The combination may be a soft combination using weight        factors which are either fixed or set according to the estimated        uplink channel conditions on respective carrier. The advantage        of this alternative is that the reliability of the downlink        power control is improved in case of frequency selective uplink        channel conditions.    -   iii. When the number of uplink carriers M is smaller than the        number of downlink carriers N to control, more than one TPC        command is to be transmitted on one uplink carrier in order to        be able to fit all TPC commands on the uplink carriers.

In the case of alternative embodiment 2 above with only one TPC commandto transmit, there will always be an available uplink carrier to use forthe transmission. However, if there are more than one uplink carriers,the reliability of the power control can be increased in case offrequency selective uplink channel conditions, according to a furtherexemplary embodiment, by transmitting the TPC command on more than oneuplink carrier. The NodeB will then adjust the transmit power of thedownlink carrier's F-DPCH according to a combination of the commandsreceived on the different uplink channels. The combination may be a softcombination using weight factors which can be either fixed or setaccording to the estimated uplink channel conditions on respectivecarrier.

In the following, the above embodiments will be further explained withreference to FIGS. 2 a-2 f. In the figures, downlink is abbreviated DLand uplink is abbreviated UL.

Starting with the alternative embodiment 1 above, and supposing amulti-carrier symmetry with two downlink carriers (one anchor carrier(A) 203 and one non-anchor carrier (NA) 204) and two uplink carriers(one anchor carrier (A) 201 and one non-anchor carrier (NA) 202), FIG. 2a illustrates how one TPC command (TPC₁) transmitted on the anchoruplink carrier 201 is used by the NodeB to adjust the transmit power ofthe anchor downlink carrier's F-DPCH 203, and one TPC command (TPC₂)transmitted on the non-anchor uplink carrier 202 is used by the NodeB toadjust the transmit power of the non-anchor downlink carrier's F-DPCH204.

Power control in a system supposing the same example of multi-carriersymmetry as above with the alternative embodiment 2, and with the commonTPC command defined according to any of the two alternatives A or Bdescribed above, is schematically illustrated in FIG. 2 b. The TPCcommand TPC₁ is transmitted on the anchor uplink carrier 201, in orderfor the NodeB to adjust the transmit power of both the anchor 203 andthe non-anchor downlink carrier's F-DPCH 204 in the same way. If TPC₁indicates “up”, then the transmit power of both downlink carriers'F-DPCH 203, 204 are adjusted by a power step “up”. The TPC₁ command mayalso be transmitted on the non-anchor uplink carrier 202 instead, asillustrated in FIG. 2 c. It is also possible, as discussed above, totransmit the TPC₁ command on both the anchor 201 and the non-anchoruplink carrier 202, in order to improve the reliability of the F-DPCHdownlink power control in case of frequency selective uplink channelconditions.

FIG. 2 d illustrates the case of the alternative embodiment 1, supposinga multi-carrier symmetry with two downlink (one anchor 203 and onenon-anchor carrier 204) and one uplink carrier 201. Two TPC commands(TPC₁ and TPC₂) are transmitted on separate control channels of the sameuplink carrier 201, as described above. The NodeB adjusts the transmitpower of the anchor downlink carrier's F-DPCH 203 according to the TPCcommand TPC₁ received on the first control channel of the anchor uplinkcarrier 201, and adjusts the transmit power of the non-anchor downlinkcarrier's F-DPCH 204 according to the TPC command TPC₂ received on thesecond control channel of the anchor uplink carrier 201.

FIG. 2 e-2 f illustrates the case of a multi-carrier symmetry with twouplink carriers (one anchor 201 and one non-anchor carrier 202) and onedownlink carrier 203. In this case there will only be one TPC command,as there is only one downlink carrier to control, so there is nodifference between alternative embodiment 1 and 2. The TPC command TPC₁is in FIG. 2 e transmitted on the control channel of the anchor uplinkcarrier 201, in order for the NodeB to adjust the downlink carrier'sF-DPCH. It is also possible to transmit TPC₁ on the control channel ofthe non-anchor uplink carrier 202 instead.

In order to improve the reliability of the downlink power control incase of frequency selective uplink channel conditions, and according toFIG. 2 f, the TPC command TPC₁ is transmitted both on the controlchannel of the non-anchor uplink carrier 202 and on the control channelof the anchor uplink carrier 201. The NodeB will then adjust thedownlink transmit power for the downlink carrier's F-DPCH 203 accordingto the soft combination of command TPC₁ received on the control channelof the anchor uplink carrier 201 (referred to as TPC_(1A)) and commandTPC₁ received on the control channel of the non-anchor uplink carrier202 (referred to as TPC_(1NA)) as follows: TPC₁combined=a1*TPC_(1A)+a2*TPC_(1NA), where a1 and a2 are real valuedweight factors which can be either fixed or set according to estimateduplink channel conditions on respective carrier.

All embodiments of the present invention are applicable during softhandover as well as during non-soft handover. The same principles arefollowed regardless of the handover scenario. In soft handover thedefined TPC commands will be received by multiple NodeBs. Thus, assumingthe same multi-carrier symmetry for all NodeBs, the way of adjusting thetransmit power of the different NodeBs F-DPCH based on the TPC commandsis the same in soft handover as in non-soft handover.

FIG. 3 a is a flowchart of the method for the UE, according to oneembodiment of the present invention. In step 301 the UE defines at leastone TPC command to be used by the NodeB for adjusting the transmit powerof the at least one downlink carrier's F-DPCH. In the next step 302 theUE transmits the defined TPC command(s) on at least one of the uplinkcarriers.

Furthermore, FIG. 3 b is a flowchart of the method for the NodeB,according to one embodiment of the present invention. In step 303, theNodeB receives the TPC command(s) on at least one of the uplinkcarriers, from the UE. In the next step 304 the NodeB adjusts thetransmit power of the at least one downlink carrier's F-DPCH based onthe received TPC command(s).

FIG. 3 c is a flowchart of the method for the UE, according toalternative embodiment 1 above. In step 301 the UE defines N TPCcommands to be used by the NodeB for adjusting the transmit power of theF-DPCH on the N downlink carriers respectively. Depending on themulti-carrier symmetry, i.e. the number of uplink carriers M, determinedin step 311, in relation to the number of downlink carriers or TPCcommands N, the step of transmitting 302 the N TPC commands comprisesthe sub step:

-   -   M<N: Transmitting, in step 312, more than one TPC commands on        the first uplink carrier and the remaining TPC commands on        separate subsequent uplink carriers. This is done in order to        fit all N TPC commands onto the M uplink carriers.    -   M=N: Transmitting, in step 313, each TPC command on a separate        uplink carrier.    -   M>N: Transmitting, in step 313, each TPC command on a separate        uplink carrier and transmitting, in step 314, a first of the N        TPC commands on at least one more uplink carrier. This is done        in order to enhance the reliability of the power control of the        F-DPCH on the first downlink carrier in case of frequency        selective uplink channel conditions (carriers need not to be        adjacent in the frequency band). This first TPC command could        for example be the TPC command corresponding to the anchor        downlink carrier's F-DPCH. It is also possible to only transmit        each TPC commands on a separate uplink carrier, as in step 313.        Some uplink carriers will then not carry any TPC command, thus        saving signaling capacity.

Furthermore, FIG. 3 d is a flowchart of the method for the NodeB,according to one example of alternative embodiment 1 above. The step 303of receiving (see FIG. 3 b) the N TPC commands will in this embodimentalso depend on the multi-carrier symmetry, i.e. the number of uplinkcarriers M, determined in step 320, in relation to the number ofdownlink carriers or TPC commands N, and will thus comprise thefollowing sub step:

-   -   M<N: Receiving, in step 321, more than one TPC commands on the        first uplink carrier and the remaining TPC commands on separate        subsequent uplink carriers. The first TPC command can in this        case be used to adjust, in step 326, the transmit power of the        first downlink carrier's F-DPCH without any combining step.    -   M=N: Receiving, in step 322, each TPC command on a separate        uplink carrier. Also in this case the first TPC command can be        used to adjust, in step 326, the transmit power of the first        downlink carrier's F-DPCH without any combining step.    -   M>N: Also here each TPC command is received on a separate uplink        carrier as in step 322, but the first of the N TPC commands is        also received, in step 323, on more than one uplink carrier. A        combination step 324 is thus needed before the step 325 of        adjusting the transmit power of the first downlink carrier's        F-DPCH based on the combined TPC command.

The last step 327 is the adjustment of the transmit power of theremaining downlink carriers' F-DPCH based on the remaining received TPCcommands separately, which is thus done regardless of if M is largerthan, equal to or smaller than N.

FIG. 3 e is a flowchart of the method for the UE, according toalternative embodiment 2 above, when the number of uplink carriers M islarger than one. In step 301 the UE defines one common TPC command to beused by the NodeB for adjusting the transmit power of the N downlinkcarriers' F-DPCH. This definition of a common TPC command can be doneaccording to either the first alternative embodiment A or the secondalternative embodiment B described above. The UE then transmits, in step331, the common TPC command on one of the M uplink carriers, and inorder to enhance the reliability of the power control of the F-DPCH onthe first downlink carrier in case of frequency selective uplink channelconditions, it also transmits, in step 332, the common TPC command on atleast a second uplink carrier.

Furthermore, FIG. 3 f is a flowchart of the method for the NodeB,according to alternative embodiment 2 above, when the number of uplinkcarriers M is larger than one. In step 340, the NodeB receives thecommon TPC command on one of the M uplink carriers, from the UE. Howeverit also receives, in step 341, the common TPC command on at least asecond uplink carrier. This means that the NodeB must combine, in step342, the TPC commands received on the different uplink carriers, beforeit can adjust, in step 343, the transmit power of the downlink carriers'F-DPCH based on the combined common TPC command.

Schematically illustrated in FIG. 4 and according to one embodiment, theUE 150 comprises means for defining 401 one or more TPC commands to beused by the NodeB for adjusting the transmit power of the downlinkcarriers' F-DPCH. It also comprises means for transmitting 402 thedefined TPC command(s) on the uplink carriers.

Also illustrated in FIG. 4 is the NodeB 130. It comprises means forreceiving 403 one or more TPC commands on the uplink carriers from theUE. It also comprises means for adjusting 404 the transmit power of thedownlink carriers' F-DPCH based on the received TPC command(s).

It should be noted that the means illustrated in FIG. 4 may beimplemented by physical or logical entities using software functioningin conjunction with a programmed microprocessor or general purposecomputer, and/or using an application specific integrated circuit(ASIC).

The above mentioned and described embodiments are only given as examplesand should not be limiting to the present invention. Other solutions,uses, objectives, and functions within the scope of the invention asclaimed in the accompanying patent claims should be apparent for theperson skilled in the art.

The invention claimed is:
 1. A method of downlink transmit power control(TPC) in a radio base station of a multi-carrier wireless communicationsystem, wherein the radio base station transmits on N downlink carriersand receives on M uplink carriers in communication with at least oneuser equipment, and wherein N and M are integers and the sum of N and Mis equal to or larger than three, said method comprising the steps of:receiving a TPC command on at least one of the M uplink carriers fromthe at least one user equipment, the number of received TPC commandsbeing equal to N, the receiving step comprising the sub steps of:receiving both a first and at least a second of said N TPC commands on afirst uplink carrier while receiving each of the remaining TPC commandson separate subsequent uplink carriers from the at least one userequipment, when M is smaller than N; and receiving the N TPC commands onseparate uplink carriers from the at least one user equipment, when M islarger than or equal to N; and adjusting a transmit power of afractional downlink control channel (FDPCH) on the N downlink carriersbased on the received at least one TPC command.
 2. The method accordingto claim 1, wherein said at least one TPC command is received on atleast one uplink control channel of said M uplink carriers.
 3. Themethod according to claim 1, wherein the step of adjusting the transmitpower of the F-DPCH on the N downlink carriers includes the sub step ofadjusting the transmit power of each F-DPCH of the N downlink carriersbased on each of the received N TPC commands separately.
 4. The methodaccording to claim 1, wherein the step of receiving the N TPC commandson at least one of the M uplink carriers also comprises the sub step ofreceiving the first of the N TPC commands also on at least a seconduplink carrier, when M is larger than N, and wherein the step ofadjusting the transmit power of the F-DPCH of the N downlink carrierscomprises the sub steps of: combining the first of the N TPC commandsreceived on the first uplink carrier and on at least a second uplinkcarrier according to a soft combining rule, when M is larger than N;adjusting the transmit power of the F-DPCH of the first downlink carrierbased on the combined TPC command, when M is larger than N; adjustingthe transmit power of the F-DPCH of the first downlink carrier based onthe first of the received N TPC commands when M is equal to or smallerthan N; and adjusting the transmit power of the F-DPCH of each of theremaining downlink carriers based on the remaining received TPC commandsseparately.
 5. A method of downlink transmit power control (TPC) in aradio base station of a multi-carrier wireless communication system,wherein the radio base station transmits on N downlink carriers andreceives on M uplink carriers in communication with at least one userequipment, and wherein N and M are integers and the sum of N and M isequal to or larger than three, said method comprising the steps of:receiving a common TPC command on a first and a second one of the Muplink carriers from the at least one user equipment; and adjusting thetransmit power of a fractional downlink control channel (F-DPCH) on theN downlink carriers based on the received common TPC command.
 6. Themethod according to claim 5, wherein the step of adjusting the transmitpower comprises the sub steps of: combining each of said common TPCcommand received on one and on at least the second of the M uplinkcarriers into a combined common TPC command according to a softcombining rule; and adjusting the transmit power of the F-DPCH of the Ndownlink carriers based on the combined common TPC command.
 7. A radiobase station of a multi-carrier wireless communication system, whereinthe radio base station is configured to transmit on N downlink carriersand receive on M uplink carriers in communication with at least one userequipment, and wherein N and M are integers and the sum of N and M isequal to or larger than three, said radio base station comprising aprogrammed processor executing software instructions, wherein when theprocessor executes the software instructions, the radio base station iscaused to perform the following: receive at least one transmit powercontrol (TPC) command on at least one of the M uplink carriers from theat least one user equipment, the number of received TPC commands beingequal to N; and adjust a transmit power of a fractional downlink controlchannel (F-DPCH) on the N downlink carriers based on the received atleast one TPC command; wherein the radio base station is configured to:receive both a first and at least a second of said N TPC commands on afirst uplink carrier and to receive each of the remaining TPC commandson separate, subsequent uplink carriers from the at least one userequipment, when M is smaller than N; and receive the N TPC commands onseparate uplink carriers from the at least one user equipment, when M islarger than or equal to N.
 8. The radio base station according to claim7, wherein the radio base station is configured to adjust the transmitpower of the F-DPCH on the N downlink carriers by adjusting the transmitpower of each of the downlink carriers' F-DPCH based on each of thereceived N TPC commands separately.
 9. The radio base station accordingto claim 7, wherein the radio base station is configured to receive theN TPC commands on at least one of the M uplink carriers by: receivingthe first of said N TPC commands also on at least a second uplinkcarrier, when M is larger than N; and wherein the radio base station isconfigured to adjust the transmit power of the F-DPCH on the N downlinkcarriers by: combining the first of said N TPC commands received both onthe first uplink carrier and on at least a second uplink carrieraccording to a soft combining rule, when M is larger than N; adjustingthe transmit power of the F-DPCH of the first downlink carrier based onthe combined TPC command, when M is larger than N; adjusting thetransmit power of the F-DPCH of the first downlink carrier based on thefirst of the received N TPC commands, when M is equal to or smaller thanN; and adjusting the transmit power of each F-DPCH of the remainingdownlink carriers based on the remaining received TPC commandsseparately.
 10. A radio base station of a multi-carrier wirelesscommunication system, wherein the radio base station is arranged totransmit on N downlink carriers and receive on M uplink carriers incommunication with at least one user equipment, and wherein N and M areintegers and the sum of N and M is equal to or larger than three, saidradio base station comprising: a programmed processor executing softwareinstructions, wherein when the processor executes the softwareinstructions, the radio base station is caused to perform the followingsteps: receiving a common transmit power control (TPC) command on afirst and a second one of the M uplink carriers from the at least oneuser equipment; and adjusting the transmit power of the fractionaldownlink control channel, F-DPCH, on the N downlink carriers based onthe received common TPC command.
 11. The radio base station according toclaim 10, wherein the software instructions include instructions foradjusting the transmit power of the N downlink carriers' F-DPCH based onsaid common TPC command.
 12. The radio base station according to claim10, wherein the software instructions include instructions for adjustingthe transmit power by: combining the common TPC command received on thefirst and second M uplink carriers into a combined common TPC commandaccording to a soft combining rule; and adjusting the transmit power ofthe F-DPCH of the N downlink carriers based on the combined common TPCcommand.
 13. A method of downlink transmit power control in amulti-carrier wireless communication system, wherein a user equipment,UE, receives on N downlink carriers and transmits on M uplink carriersin communication with a radio base station, wherein N and M are integersand the sum of N and M is equal to or larger than three, said methodcomprising the steps of: defining by the UE, at least one transmit powercontrol (TPC) command to be used by the radio base station for adjustinga transmit power of a fractional downlink physical control channel(F-DPCH) on the N downlink carriers, the number of defined TPC commandsbeing equal to N; transmitting by the UE, the N TPC commands on at leastone of the M uplink carriers, the transmitting step comprising the substeps of: transmitting both a first and at least a second of said N TPCcommands on a first uplink carrier and each of the remaining TPCcommands on separate subsequent uplink carriers, in order to fit all NTPC commands onto the M uplink carriers when M is smaller than N; andtransmitting each of said N TPC commands on separate uplink carrierswhen M is larger than or equal to N; receiving by the base station, theN TPC commands on at least one of the M uplink carriers from the UE, thereceiving step comprising the sub steps of: receiving both the first andat least the second of the N TPC commands on a first uplink carrierwhile receiving each of the remaining TPC commands on separatesubsequent uplink carriers from the UE, when M is smaller than N; andreceiving the N TPC commands on separate uplink carriers from the UE,when M is larger than or equal to N; and adjusting by the base station,the transmit power of the F-DPCH on the N downlink carriers based on thereceived at least one TPC command.
 14. A method of downlink transmitpower control in a multi-carrier wireless communication system, whereina user equipment (UE) receives on N downlink carriers and transmits on Muplink carriers in communication with a radio base station, wherein Nand M are integers and the sum of N and M is equal to or larger thanthree, said method comprising the steps of: defining by the UE, a commontransmit power control (TPC) command to be used by the radio basestation for adjusting a transmit power of a fractional downlink physicalcontrol channel (F-DPCH) on the N downlink carriers; transmitting by theUE, the common TPC command on a first and a second one of the M uplinkcarriers; receiving by the base station, the common TPC command on thefirst and second M uplink carriers from the UE; and adjusting by thebase station, the transmit power of the F-DPCH on the N downlinkcarriers based on the received common TPC command.